1. Field of the Invention
The present invention relates to an ink absorber for use in an inkjet recorder having an ink-ejection type recording head, an ink-wetted member such as an ink tank, an inkjet cartridge, and the like, as well as to ink.
2. Description of the Related Art
A hitherto-known, so-called inkjet recorder has a recording head of ink ejection type provided with ejection ports for ejecting ink, and ejects ink in the form of ink droplets from the recording head to thus cause the ink to adhere to a sheet, thereby recording an image. The inkjet recorder has an ink tank for storing ink, and ink is supplied from the ink tank to the recording head. A member which remains in wetted contact with ink at all times has heretofore been formed from resin materials, metallic materials, rubber materials, and the like. In view of cost and ease of processing, resin materials are often used. Example resin materials include polyolefins such as polypropylene and polyethylene, polyvinyl chloride, polyvinylidene chloride, silicone, an ethylene-vinyl acetate copolymer, ABS, polyacetal, nylon, unsaturated polyester, aramid, PS, PET, PVC, and the like. In view of environmentally-friendly recycling, polyolefin such as polypropylene and polyethylene is preferably used.
There may be a case where antioxidant is added to a resin material in order to prevent decomposition and deterioration of the resin material, which would otherwise be caused when the resin material is oxidized by heat, light, oxygen, or the like, during or after the process of manufacturing or processing the resin material. In order to capture radicals which grow during a stage of initial chain growth induced by auto-oxidation of a resin material, in a known technique an antioxidant (e.g., phenolic antioxidant, amine-based antioxidant, phosphorus antioxidant, thioether oxidant) has been added.
In relation to a material having a high degree of crystallinity such as polyolefin; e.g., polypropylene, polyethylene, and the like; particularly, polypropylene, crystal of a molded article is generally nonuniform, scatters light, and exhibits insufficient transparency. In order to generate a minute, uniform crystal, a bis(p-methylbenzylidene)sorbitol (trade name: Gelol MD) has hitherto been known to be added as a crystallization nucleating agent.
A catalyst, such as a Ziegler-Natta catalyst, is usually used for polymerization of olefin during manufacture of polyolefin such as polypropylene, polyethylene, and the like. Residuals of catalyst, such as chlorine compounds, remain in generated polymer. The catalyst still remaining in polymer has a potential risk of corroding or degrading polymer such as yellowing of polymer. For this reason, a counteragent has been known to be added to the resultant polymer so as to react with the residual catalyst to thus neutralize the residual catalyst. Metallic salt of fatty acid, such as calcium stearate, or hydrotalcite (basic aluminum magnesium carbonate) has been known to be added as a counteragent.
Metallic salt of fatty acid, such as calcium stearate, is commonly added in an amount of 1,000 to 1,500 ppm to polymer as a counteragent for polypropylene. Using the metallic salt as the ink-wetted member has been known to generate fibrous suspended matters which in some cases will hinder flowability of ink. In order to prevent generation of fibrous suspended matters, JP-A-63-216752 proposes a method for reducing the amount of fatty acid, such as calcium stearate, to 100 ppm or less.
Japanese Patent No. 2696828 describes a method for solving a problem of suspended matters being formed by a solute originating from the ink-wetted member by means of a combination of the density of sodium ions in ink with the ink-wetted member. This method is found to be insufficient in terms of accuracy of ejection of ink achieved after the ink left for a long period of time has been brought into contact with the ink-wetted member.
In recent years, employing ink which uses a pigment as an ink coloring material for inkjet purpose has been energetically discussed. Transforming a pigment into minute particles has been proposed as a technique for realizing a pigment which enhances print quality, an ejection characteristic, storage stability, a clogging characteristic, a fixing characteristic, rubfastness, and an increase in print speed, all of which are drawbacks in pigment ink for inkjet use. For instance, JP-A-2003-3095proposes that a mean particle size of a pigment preferably ranges from 50 to 100 nm. However, this technique is not preferable in terms of inconsistencies in density and inconsistent streaks, and a further improvement in technique is sought.